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Spiral Imaging (spiral + imaging)

Distribution by Scientific Domains
Medical Sciences100%

Selected Abstracts

Application of k -space energy spectrum analysis for inherent and dynamic B0 mapping and deblurring in spiral imaging

MAGNETIC RESONANCE IN MEDICINE, Issue 4 2010
Trong-Kha Truong
Abstract Spiral imaging is vulnerable to spatial and temporal variations of the amplitude of the static magnetic field (B0) caused by susceptibility effects, eddy currents, chemical shifts, subject motion, physiological noise, and system instabilities, resulting in image blurring. Here, a novel off-resonance correction method is proposed to address these issues. A k -space energy spectrum analysis algorithm is first applied to inherently and dynamically generate a B0 map from the k -space data at each time point, without requiring any additional data acquisition, pulse sequence modification, or phase unwrapping. A simulated phase evolution rewinding algorithm and an automatic residual deblurring algorithm are then used to correct for the blurring caused by both spatial and temporal B0 variations, resulting in a high spatial and temporal fidelity. This method is validated against conventional B0 mapping and deblurring methods, and its advantages for dynamic MRI applications are demonstrated in functional MRI studies. Magn Reson Med, 2010. © 2010 Wiley-Liss, Inc. [source]

Ultrafast imaging: Principles, pitfalls, solutions, and applications

JOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 2 2010
Jeffrey Tsao PhD
Abstract Ultrafast MRI refers to efficient scan techniques that use a high percentage of the scan time for data acquisition. Often, they are used to achieve short scan duration ranging from sub-second to several seconds. Alternatively, they may form basic components of longer scans that may be more robust or have higher image quality. Several important applications use ultrafast imaging, including real-time dynamic imaging, myocardial perfusion imaging, high-resolution coronary imaging, functional neuroimaging, diffusion imaging, and whole-body scanning. Over the years, echo-planar imaging (EPI) and spiral imaging have been the main ultrafast techniques, and they will be the focus of the review. In practice, there are important challenges with these techniques, as it is easy to push imaging speed too far, resulting in images of a nondiagnostic quality. Thus, it is important to understand and balance the trade-off between speed and image quality. The purpose of this review is to describe how ultrafast imaging works, the potential pitfalls, current solutions to overcome the challenges, and the key applications. J. Magn. Reson. Imaging 2010;32:252,266. © 2010 Wiley-Liss, Inc. [source]

Application of k -space energy spectrum analysis for inherent and dynamic B0 mapping and deblurring in spiral imaging

MAGNETIC RESONANCE IN MEDICINE, Issue 4 2010
Trong-Kha Truong
Abstract Spiral imaging is vulnerable to spatial and temporal variations of the amplitude of the static magnetic field (B0) caused by susceptibility effects, eddy currents, chemical shifts, subject motion, physiological noise, and system instabilities, resulting in image blurring. Here, a novel off-resonance correction method is proposed to address these issues. A k -space energy spectrum analysis algorithm is first applied to inherently and dynamically generate a B0 map from the k -space data at each time point, without requiring any additional data acquisition, pulse sequence modification, or phase unwrapping. A simulated phase evolution rewinding algorithm and an automatic residual deblurring algorithm are then used to correct for the blurring caused by both spatial and temporal B0 variations, resulting in a high spatial and temporal fidelity. This method is validated against conventional B0 mapping and deblurring methods, and its advantages for dynamic MRI applications are demonstrated in functional MRI studies. Magn Reson Med, 2010. © 2010 Wiley-Liss, Inc. [source]

An efficient gridding reconstruction method for multishot non-Cartesian imaging with correction of off-resonance artifacts

MAGNETIC RESONANCE IN MEDICINE, Issue 6 2010
Yuguang Meng
Abstract An efficient iterative gridding reconstruction method with correction of off-resonance artifacts was developed, which is especially tailored for multiple-shot non-Cartesian imaging. The novelty of the method lies in that the transformation matrix for gridding (T) was constructed as the convolution of two sparse matrices, among which the former is determined by the sampling interval and the spatial distribution of the off-resonance frequencies and the latter by the sampling trajectory and the target grid in the Cartesian space. The resulting T matrix is also sparse and can be solved efficiently with the iterative conjugate gradient algorithm. It was shown that, with the proposed method, the reconstruction speed in multiple-shot non-Cartesian imaging can be improved significantly while retaining high reconstruction fidelity. More important, the method proposed allows tradeoff between the accuracy and the computation time of reconstruction, making customization of the use of such a method in different applications possible. The performance of the proposed method was demonstrated by numerical simulation and multiple-shot spiral imaging on rat brain at 4.7 T. Magn Reson Med, 2010. © 2010 Wiley-Liss, Inc. [source]

Novel interleaved spiral imaging motion correction technique using orbital navigators

MAGNETIC RESONANCE IN MEDICINE, Issue 2 2003
Hisamoto Moriguchi
Abstract Although spiral imaging seldom produces apparent artifacts related to flow, it remains sensitive to rapid object motion. In this article, a new correction method is presented for rapid rigid body motion in interleaved spiral imaging. With this technique, an identical circular navigator k -space trajectory is linked to each spiral trajectory. Data inconsistency due to both rotation and translation among spiral interleaves can be corrected by evaluating the magnitudes and phases of the data contained in the navigator "ring." Further, it is difficult to create a frequency field map for off-resonance correction when an object moves during a scan, because there is motion-dependent misregistration between the two images acquired with different TEs. However, this difficulty can be overcome by combining the motion-correction method with a recently proposed technique (off-resonance correction using variable-density spirals (ORC-VDS)), thereby enabling both motion compensation and off-resonance correction with no additional scanning. Magn Reson Med 50:423,428, 2003. © 2003 Wiley-Liss, Inc. [source]